When a public power grid suddenly stops supplying power, a distributed photovoltaic power generation system connected with the power grid cannot detect the power failure state of the power grid in time and continues working, thereby forming a self-powered island. The photovoltaic power generation system will produce serious consequences in an island operation state, for example, the voltage and frequency in the island cannot be controlled, which may damage users' equipment; a circuit in the island is still electrified, which may endanger the personal safety of maintenance personnel; the action timing sequence of protection switches of the power grid system is affected; and when the electric power company recovers the power supply, a large impact current is generated due to phase asynchrony, and so on. At present, corresponding anti-island protection performance detection standards and detection flows are formulated both at home and abroad.
At present, in the field of anti-island protection performance detection at home and abroad, only the magnitude and a single interval of fundamental current flowing through a grid connection switch are considered in initial test conditions, resulting in that a part of inverters cannot correctly reflect the anti-island ability of the inverters with respect to characteristic load design; and meanwhile the anti-island protection performance of the inverters cannot be comprehensively and precisely reflected.